<!doctype html>
<html>
<head>
<title>Linear Gradient</title>
	<script src="../../dist/Chart.js"></script>
	<script src="../utils.js"></script>
	<style>
		canvas {
			-moz-user-select: none;
			-webkit-user-select: none;
			-ms-user-select: none;
		}
	</style>
</head>

<body>
	<div style="width: 75%;">
		<canvas id="canvas"></canvas>
	</div>
	<br>
	<br>
	<button id="randomizeData">Randomize Data</button>
	<script>
		var chartColors = window.chartColors;
		var gradient = null;
		var width = null;
		var height = null;
		var config = {
			type: 'line',
			data: {
				labels: ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
				datasets: [{
					label: 'My First dataset',
					borderColor: function(context) {
						var chartArea = context.chart.chartArea;

						if (!chartArea) {
							// This case happens on initial chart load
							return null;
						}

						var chartWidth = chartArea.right - chartArea.left;
						var chartHeight = chartArea.bottom - chartArea.top;
						if (gradient === null || width !== chartWidth || height !== chartHeight) {
							// Create the gradient because this is either the first render
							// or the size of the chart has changed
							width = chartWidth;
							height = chartHeight;
							var ctx = context.chart.ctx;
							gradient = ctx.createLinearGradient(0, chartArea.bottom, 0, chartArea.top);
							gradient.addColorStop(0, chartColors.blue);
							gradient.addColorStop(0.5, chartColors.yellow);
							gradient.addColorStop(1, chartColors.red);
						}

						return gradient;
					},
					data: [
						randomScalingFactor(),
						randomScalingFactor(),
						randomScalingFactor(),
						randomScalingFactor(),
						randomScalingFactor(),
						randomScalingFactor(),
						randomScalingFactor()
					],
					fill: false,
				}]
			},
			options: {
				responsive: true,
				title: {
					display: true,
					text: 'Chart.js Line Chart'
				},
				tooltips: {
					mode: 'index',
					intersect: false,
				},
				hover: {
					mode: 'nearest',
					intersect: true
				},
				scales: {
					x: {
						display: true,
						scaleLabel: {
							display: true,
							labelString: 'Month'
						}
					},
					y: {
						display: true,
						scaleLabel: {
							display: true,
							labelString: 'Value'
						}
					}
				}
			}
		};

		window.onload = function() {
			var ctx = document.getElementById('canvas');
			window.myPolarArea = new Chart(ctx, config);
		};

		document.getElementById('randomizeData').addEventListener('click', function() {
			config.data.datasets.forEach(function(piece, i) {
				piece.data.forEach(function(value, j) {
					config.data.datasets[i].data[j] = randomScalingFactor();
				});
			});
			window.myPolarArea.update();
		});
	</script>
</body>

</html>
